1. Field of the Invention
The present invention relates to a method for adjusting a color temperature point for a color display device, and, more particularly, to color temperature adjustment for the color display device.
2. Description of the Related Art
An ultimate goal for various display technologies is to truthfully present the captured image via the display system, which requires color temperature adjustment technology. Different light sources create different colors on objects; therefore, light changes at different locations or at different times can yield images having different color temperatures. If the display device has only a fixed color temperature output, then it will not be able to truthfully present the picture as seen by human eyes. In addition, different races tend to have different colors preferences; for example, Asians prefer warm colors, whereas Europeans prefer cold colors. Therefore, for users in different countries, some color temperature adjustments may be needed.
A prior art document “Method and device for adjusting color temperature of a color display device” (R.O.C. published patent No. 200532637) provides a method for adjusting display color temperatures, which works by setting a corresponding (x1, y1) chroma coordinates for a target color temperature on a CIE1931 xyY chromaticity diagram, and then measuring the current color temperature of the display and converting it to a corresponding (x2, y2) chroma coordinate. The direction of a vector R between (x2, y2) to (x1, y1) is then found. The standard output of red (R), green (G), and blue (R) components are adjusted according to the direction of the vector R. Finally, the color temperature of the display is re-measured to determine if the adjusted display is now close to the target color temperature so as to determine whether fine-tuning processes should be repeated. This color temperature adjustment method relies primarily on experience rather than on an accurate analysis and requires a repetitive, time-consuming adjustment process.
Another prior art document, “Liquid display color temperature automatic adjustment system and method” (R.O.C. patent No. I246319) discloses a method for adjusting a display color temperature, which involves setting predetermined x, y values for a target color temperature; measuring x, y values of the display; respectively comparing two x, y values to determine whether increasing or decreasing of the standard output of the R, G, B components is required; and repeating the measuring and adjustment processes to cause the color temperature of the display to approach the target color temperature. However, on the CIE1931 xyY chromaticity diagram, the directions from the color temperature point to R, G, B points are not parallel to the x axis or the y axis, and increasing or decreasing any standard output of the R, G, B components, both x value and y values are changed simultaneously. Therefore, this method requires repetitive measuring and comparing to approach the color temperature point, which is time consuming and does not provide accurate results.
Another prior art document, “Color correction circuit and method for a liquid display,” (R.O.C. published patent No. 200521605) discloses a method that comprises: establishing a color choosing unit having a color temperature value and gamma options; storing the color choosing unit in a read-only memory (ROM) to provide a plurality of sets of color temperature value and Gamma value (a scale between brightness and grey scale) options; after the user has selected one set, calculating a corresponding correction parameter of the selected color temperature value and gamma value using functional interpolation; and loading the correction parameter into a parameter register to correct the color temperature and gamma. This method can obtain results quicker than the previous two technologies (R.O.C. patent published No. 200532637 and R.O.C. patent No. I246319), however, it does not have an algorithm firmly based on scientific theory, and the accuracy and results are not very satisfactory.
It is therefore desirable to provide a method for adjusting color temperature that mitigates and/or obviates the aforementioned problems.